Transmission Mods

[Huskymaniac]

I have been doing a lot of reading and have attempted to compile a list of transmission modifications. I don't want to start an argument but I would like to get a list of mods that will help prolong the life of the transmission and rank them in order of their effectiveness. I am not concerned with feel or improving the 0-60. This is strictly reliability related but, of course, anything that improve both would be great. Here is what I have so far:

1. Transmission cooler
2. Transmission filter for post 1993 models
3. Upgrade valve bodies
4. Upgrade TCU with unit from ecutune.com
5. Harvey's quick change
6. Shift kit from smallcar.com
7. Remove the transmission resistor
8. Increase the resistance of the transmission resistor to 20-100 Ohms
9. Add switch to engage power mode
10. Switch to synthetic ATF

What are people's feelings about these? Which will help reliability and how would you rank them? I have read that removing the resistor or using the shift kit may actually hurt reliability. The power mode switch will change to the better shift maps but doesn't it also prevent torque converter lockup and doesn't that actually cause more heat to be generated? It would seem that the effects cancel each other at least somewhat. I'm not sure what Harvey's quick change does or how it is installed. The TCU upgrade would seem to change shift maps while still allowing lock up. It also forces lock up and sets off the warning light at a lower temperature. I don't see a drawback. The bigger valve bodies seems to be a nice upgrade but complex and expensive.

If the tranny cooler is installed between the condenser and the radiator, does it matter exactly where? High or low? Passenger side or driver side? Does it need to be attached to the radiator or is the sandwich force between the radiator and condenser enough to hold it, especially if it is a small one? Does it need to be cushioned or insulated from either?

[NeedForSpeed]

This thread should be interesting

[NiftySVX]

Messing with the transmission is a tricky business. Adding a cooler that restricts the flow will do more damage than good, and the fluid temperature isn't really an issue with these. A filter is not needed unless it is a 92 with the old torque converter, and really all of the 92s need to have their radiator replaced and converter replaced. A filter is just another possible flow restriction in the cooler circuit. The phase 1 4EAT suffers mainly from issues stemming from weak line pressure. The high clutch has a tendency to burn up, but this isn't because the fluid is hot. It slips and then superheats the fluid so the hot fluid is a symptom not the cause. Cooling fluid exiting from a burnt up clutch pack isn't going to help anything.

Disconnecting the resistor can, in some cases, allow a trans that is on its way out to last just a bit longer. But other than that, you're just going to have line pressure that is too high when at idle resulting in hard shifts.

The only real way to modify the transmission for "longer life" is to make changes to the valve body to boost main line across the board and bore out certain passages to MAKE SURE the high clutch has alot of pressure when it is applied and to make sure that fluid is draining from it when it is not applied so that it is not dragging. This is the prevailing theory, at least.

It should be noted that Subaru gave up on the design of the original 4eat and started over.

[Huskymaniac]

Originally Posted by NiftySVX

Messing with the transmission is a tricky business. Adding a cooler that restricts the flow will do more damage than good, and the fluid temperature isn't really an issue with these. A filter is not needed unless it is a 92 with the old torque converter, and really all of the 92s need to have their radiator replaced and converter replaced. A filter is just another possible flow restriction in the cooler circuit. The phase 1 4EAT suffers mainly from issues stemming from weak line pressure. The high clutch has a tendency to burn up, but this isn't because the fluid is hot. It slips and then superheats the fluid so the hot fluid is a symptom not the cause. Cooling fluid exiting from a burnt up clutch pack isn't going to help anything.

Disconnecting the resistor can, in some cases, allow a trans that is on its way out to last just a bit longer. But other than that, you're just going to have line pressure that is too high when at idle resulting in hard shifts.

The only real way to modify the transmission for "longer life" is to make changes to the valve body to boost main line across the board and bore out certain passages to MAKE SURE the high clutch has alot of pressure when it is applied and to make sure that fluid is draining from it when it is not applied so that it is not dragging. This is the prevailing theory, at least.

It should be noted that Subaru gave up on the design of the original 4eat and started over.

I hear what you are saying about the cooler. My mechanic is also hesitant to add one for much of the same logic you put forth here. But I have one add-on question. If you cool the fluid then it starts colder when it enters the high clutch so it should oxidize less since the terminal temperature when the fluid leaves the tranny should be a little lower since it started out lower before it got heated up by that clutch.

So I see that you put a new valve body as the #1 mod for extending the tranny life. Hard to argue with that. What would be your #2 mod from the list I gave? And which of the items actually don't help or hurt?

[NiftySVX]

I understand what you are saying about the fluid, but keep in mind that the clutch is going to slip regardless of the temperature of the fluid. The fluid can be 0 degrees or it can be 212 it won't make any difference. Once the clutch slips it will boil the fluid off the friction surfaces no matter what temperature it is. The problem is that there is not enough fluid, or that the fluid didn't drain fast enough, depending on the circumstance.

ATF and the transmission are designed to operate between 176 and 212 degrees. The best thing you can do is make sure the fluid is changed regularly as needed. ATF is stable to about 300f. You will never see it get that hot though, the hoses and seals would melt out long before that. The new TCU turns the light and enters overtemp mode at 212, which you will still never see, unless the fluid is overheating because a clutch pack is slipping, and at that point you don't need a light to come on to tell you your trans is shot. Or because you have overfilled it.

If you have a 92, replace the radiator or bypass it with a high flow cooler or and replace the converter, or have it rebuilt. Then once you have the fluid system clean of converter clutch material, discard the filter. This is the fix that should have been performed originally. There is also a modification to the pump body. There was a new gasket to retrofit those in service to prevent a line pressure loss.

The rest of the modifications you mention will have effect on the operation of the transmission but will be highly unlikely to have any effect to extend the life of the unit. This is debatable, to some extent, but no modification to the resistor in the solenoid A circuit or to the shift maps is going to make a serious difference.

As far as synthetic fluid goes, it's a waste of money in my opinion. Again, it won't do you any good when your line pressure is too low and the clutch slips. The best fluid in the world won't do you any good at that point, unless they can come up with one that repairs friction discs

[Huskymaniac]

I have a 1996. The last time I looked, the fluid still looked good. I'm not sure what, if anything, I should do for this tranny. I have read wildly varying opinions. Some say a cooler is a must have, even for a 1996. Some say the same for a filter. Others say to just change the fluid regularly and the mods are unnecessary.

[svxfiles]

Your list;
1. Transmission cooler
2. Transmission filter for post 1993 models
3. Upgrade valve bodies
4. Upgrade TCU with unit from ecutune.com
5. Harvey's quick change
6. Shift kit from smallcar.com
7. Remove the transmission resistor
8. Increase the resistance of the transmission resistor to 20-100 Ohms
9. Add switch to engage power mode
10. Switch to synthetic ATF

I have done everything here on my personal SVXi except #2 & #9.
I will not add a filter to my 4EAT and restrict flow!
And not #9, cuz I haven't had any free time.

In my humble opinion the best thing that you can do for the life of your SVX transmission is to remove/delete the factory in radiator cooler/warmer!
Take the hoses off of it and just try blowing through it and you will see what I am talking about!
Any Hayden/Imperial cooler sandwiched between the radiator and the AC condenser will improve flow!

The upgraded valve body is only $350.00 for the part plus installation.
I think thats cheap!
We are not talking about a freekin Chevy here!
BTW I have one car here with the ECUTune valve body, come here and drive it.
I have two cars here with the ECUTune TCM here come drive them.

I have several Small Car kits here as take offs.
Come here, install one and report back for others!


Unplugging the resister gives a code.

I used to change about 1/2 my ATF every 6000 miles.
Switched to B G Products and have not switched back in about six years.

Out of everything on this list the only two that improve flow are replacing the valve body with a modified one, and getting rid of the factory cooler.
ATF flow is the most important thing for the life of your 4EAT!

[Huskymaniac]

Tom,

Does the flow through the stock cooler hold for all SVXs or just the older ones with the clogged screens? It is surprising that a double pass cooler could be so restrictive. If one bypasses the stock cooler, I would have to imagine that one would want a high capacity cooler. What size/capacity would you suggest? The one thing that concerns me is the airflow restriction that a large cooler would cause if sandwiched between the condenser and the radiator.

On the valve bodies, they are $350 but what can I expect for labor costs and won't I have to ship them my old valve bodies and wait to get them back? Thanks for the input.

[Huskymaniac]

Originally Posted by NiftySVX

I understand what you are saying about the fluid, but keep in mind that the clutch is going to slip regardless of the temperature of the fluid. The fluid can be 0 degrees or it can be 212 it won't make any difference. Once the clutch slips it will boil the fluid off the friction surfaces no matter what temperature it is. The problem is that there is not enough fluid, or that the fluid didn't drain fast enough, depending on the circumstance.

So would improving flow by putting in a less restrictive cooler help get enough fluid in there to prevent slippage? How much heat do those plates generate in order to take a fluid at 0C and instantly boil it?!?!?!

ATF and the transmission are designed to operate between 176 and 212 degrees. The best thing you can do is make sure the fluid is changed regularly as needed.

So are you saying that a healthy transmission does not have a slipping clutch pack and, if I change the ATF regularly, it probably won't start slipping? Of course, I am also assuming that I can't beat on the car, which I don't and won't.

ATF is stable to about 300f. You will never see it get that hot though, the hoses and seals would melt out long before that. The new TCU turns the light and enters overtemp mode at 212, which you will still never see, unless the fluid is overheating because a clutch pack is slipping, and at that point you don't need a light to come on to tell you your trans is shot. Or because you have overfilled it.

Let's assume that we only have the stock cooler in the circuit. I believe it is normal for the engine temp to rise into the 190s and even a little higher in hot environments and stop and go traffic or on a hill climb. Won't that heat the fluid up to the 190s, or higher, as it goes through the stock cooler which shares the same radiator as the engine coolant? And, if it starts that high, won't the ATF temperatures rise well into the 200s as it passes through the tranny?

The rest of the modifications you mention will have effect on the operation of the transmission but will be highly unlikely to have any effect to extend the life of the unit. This is debatable, to some extent, but no modification to the resistor in the solenoid A circuit or to the shift maps is going to make a serious difference.

As far as synthetic fluid goes, it's a waste of money in my opinion. Again, it won't do you any good when your line pressure is too low and the clutch slips. The best fluid in the world won't do you any good at that point, unless they can come up with one that repairs friction discs

OK, I got the message about a slipping tranny being beyond repair short of an actual rebuild. But, assuming it isn't slipping, won't a resistor increase cause the line pressure to be a little higher and help avoid a slip from developing?

On synthetics, won't using them also help to avoid developing a slip? Actually, what really causes a slip to develop? You mentioned earlier that not enough fluid or the fluid not draining fast enough is the root problem. If that occurs, what mechanism then causes the clutch discs to start slipping? I was under the impression that the ATF fluid overheats. That causes it to oxidize. It then either loses its ability to lubricate and/or it starts to coat the tranny parts with crap. The crap then causes it to slip. So, if one can keep it from overheating the fluid, one can help to avoid this chain of events. By overheating, I mean the level of heat that causes the tranny fluid to oxidize rapidly and not the crazy heat you mentioned once a slip has developed. I picture this as a vicious cycle that has to be broken or brought under control. The ATF heats up which causes it to oxidize which causes it to not lubricate as well which causes the tranny to generate more heat which causes the ATF to heat to an even higher temperature and so on until the temperature gets so high that parts start to get coated with crap from the overheated ATF.

Changing the fluid regularly will keep fresh, non oxidized, fluid in there to keep things lubed properly and keep the temperature from ever getting to that critical temperature. I would think synthetic fluids would oxidize slower so it will stay fresher between ATF changes and keep one from getting to that critical temperature. Also, ester based synthetics supposedly help heat transfer to keep temperatures lower. Cooling the fluid better, with a better external cooler, should also help slow down this process and keep one from getting to that critical temperature. And, of course, getting better fluid flow would help since it helps to keep parts cool and avoid the overheating based oxidation in the first place. As you and Tom mentioned, the valve bodies would help there along with, perhaps, a less restrictive cooler.

[svxfiles]

Originally Posted by Huskymaniac

Tom,

1)Does the flow through the stock cooler hold for all SVXs or just the older ones with the clogged screens?
2)It is surprising that a double pass cooler could be so restrictive. If one bypasses the stock cooler, I would have to imagine that one would want a high capacity cooler.
3)What size/capacity would you suggest?
4)The one thing that concerns me is the airflow restriction that a large cooler would cause if sandwiched between the condenser and the radiator.

5)On the valve bodies, they are $350 but what can I expect for labor costs and won't I have to ship them my old valve bodies and wait to get them back? Thanks for the input.

1) All years.
2) The factory ATF cooler is a single pass hollow brass tube about 12" long.
3) It depends on alot of things.
Climate, transmission condition, driving style, driving conditions, traffic, etc.
The best way to determine the cooler size is to find out what your transmission temperature is now.
Too big and you will never get torque converter lock up,
too small anf you are only mildly better than the factory set up!
More on this later.
4) On my hottest running SVX, the one with a 7-11 PSI blower, I was running a huge cooler, maybe 15" X 11", and before the hi flow ECUTune valve body it kept my ATF to no more than 190°f on a 100°f day, while dragracing or autocrossing.
BTW, even with a huge cooler, properly mounted airflow is not a problem.
5) I will have to estimate this one...
Raise the car, drain the ATF, drop the 20 bolt pan, drop the filter, carefully drop the valve body, take the new valve body, using a trans jack, carefully reinstalling the VB, filter and pan, refill trans.


Here is a copy of my bill to change out a valve body for a recent customer.
I hope that this helps.
Jeremy Weimer 07-01-10
1996 Subaru Outback Wagon Green
Install customer's valve body.
Thursday;
3:15-5:15
Labor------------------------------------------------------$90.00
FelPro transmission pan gasket------------------------$10.00
Shop fee----------------------------------------------------$5.00
Misc. brackets and bolts------------------------------------NC
Tax----------------------------------------------------------$6.30
Total------------------------------------------------------$111.30

[NiftySVX]

Like SVXfiles said the enemy here is line pressure. The atf contains a friction modifier. it is what actually does the "sticking" in the clutch packs. Theoretically, and in a properly operating trans, you can remove the friction discs after 100,000 miles and they will look brand new. ANY slip, even a little bit, will wear through the clutch plates almost immediately. If you ever put pressure aginst the piston and there is no or not enough fluid on the plates, they will slip. There is also a guess by some of us that the high clutch is partially engaged at times that it shouldn't be and is causing it to slip.

The resistor may help, I'm not really sure, it's not clear what the exact problem is with the trans, and the resistor only boosts line at about 10% throttle or less. Really, if you want to make a change to line pressure you need to do it in the valve body, because that's where the hydraulic circuit is. Removing the resistor only changes the TCU's ability to control the duty A solenoid that regulates line pressure. It won't help with the other parts of the hydraulic circuit, such as the passage that leads to the back of the apply piston for the high clutch.

[NiftySVX]

By the way, if you want to see the cooler I am using on my level 10 trans check out the thread that can be found by searching "the ultimate trans cooler"

There is no possibility of restricting the circuit with that one, as it flows more than the pipes going to it.

And the fluid "cooler" in the radiator is more of a "temperature stabilizer" because it is in contact with the coolant. The idea is to keep the atf near coolant temp which as you mentioned runs between 190 and 212. (230 is the red on the gauge, fans will come on around 210 or so)

[Huskymaniac]

Originally Posted by svxfiles

1) All years.
2) The factory ATF cooler is a single pass hollow brass tube about 12" long.
3) It depends on alot of things.
Climate, transmission condition, driving style, driving conditions, traffic, etc.
The best way to determine the cooler size is to find out what your transmission temperature is now.
Too big and you will never get torque converter lock up,
too small anf you are only mildly better than the factory set up!
More on this later.
4) On my hottest running SVX, the one with a 7-11 PSI blower, I was running a huge cooler, maybe 15" X 11", and before the hi flow ECUTune valve body it kept my ATF to no more than 190°f on a 100°f day, while dragracing or autocrossing.
BTW, even with a huge cooler, properly mounted airflow is not a problem.
5) I will have to estimate this one...
Raise the car, drain the ATF, drop the 20 bolt pan, drop the filter, carefully drop the valve body, take the new valve body, using a trans jack, carefully reinstalling the VB, filter and pan, refill trans.

Based on 2 hours of labor, it would probably cost me about $150. So the full cost is $500. That's enough to make me take pause as we have spent a lot of money on car maintenance the last couple of months. Since winter is coming, maybe I should consider the valve body job in the spring. How do I deal with the core thing? Do I send him the old one once it is taken out?

On climate, it sucks here in upstate NY. It can get up to 100F in the summer and down to -30F in the winter. I think the tranny is currently in good condition. It shifts smoothly without noticeable slip or any kind of jarring. Not sure what all that means for the suggested cooling capacity of an external cooler. Any suggestions would be greatly appreciated.

When I talked about restricting air flow, I wasn't concerned about how high the tranny temp would get. I am more concerned about how high the engine temp will get as a result of sticking another large object in front of the radiator. The engine temps already run pretty high when it is hot outside. It would suck to trade a tranny failure for a...you know what.

Thanks guys, this is a really good discussion. I have already decided to not install my cooler and wait until spring to install a bigger one. By the way, why not run it in parallel versus bypassing the stock cooler in the radiator? The new cooler will be low flow resistance so most of the ATF will flow through it anyways. Seems like a little ATF flow through the stock cooler couldn't hurt.

[Sean486]

Does the ECUTune valve body upgrade result in any improved feel to the transmission or is it all about flow of ATF?

[svxfiles]

Originally Posted by Sean486

Does the ECUTune valve body upgrade result in any improved feel to the transmission or is it all about flow of ATF?

YES!
The amount of time elapsed during the actual shift is reduced by about 1/2!
The shifts are MUCH more firm, and what am I doing awake at this unGodly hour?